Current collector, electrode plate including the same and electrochemical device

ABSTRACT

The present disclosure relates to the technical field of battery, and in particular, relates to a current collector, an electrode plate including the current collector, and an electrochemical device. The current collector includes an insulation layer; and a conductive layer at least located on at least one surface of the insulation layer. The conductive layer has a thickness of D2, where 30 nm≤D2≤3 μm. The current collector is provided with a plurality of holes penetrating through the insulation layer and the conductive layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Chinese Patent ApplicationNo. CN201810290303.X, filed on Mar. 30, 2018, the content of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to the technical field of battery, and inparticular, relates to a current collector, an electrode plate includingthe current collector, and an electrochemical device.

BACKGROUND

Lithium-ion batteries have been widely applied in electric vehicles andconsumer electronic products due to their advantages such as high energydensity, high output power, long cycle life, and low environmentalpollution. However, when lithium-ion batteries are subjected to abnormalconditions such as extrusion, collision, or puncture, they can easilycatch fire or explode, causing serious problems. Therefore, the safetyissue of the lithium-ion batteries greatly limits the application ofdisclosure and popularization of the lithium-ion batteries.

A large number of experimental results show that an internal shortcircuit in a battery is the ultimate cause of safety hazards of thelithium-ion batteries. In order to avoid the internal short circuit inthe battery, the researchers tried to improve the separator structure,battery mechanical structure and the like. Some of these studies haveimproved the safety performance of lithium-ion batteries by modifyingthe design of current collectors.

The temperature in the battery may rise when an internal short circuitoccurs in the battery due to abnormal conditions such as collision,extrusion, or puncture and the like. According to a technical solutionin the related art, alloy having a low melting point is added into thematerial of a metal current collector. With increasing of thetemperature of the battery, the alloy having low-melting point in thecurrent collector begins to melt, thereby resulting in a broken circuitof an electrode plate and cutting off the current. In this way, thesafety of the battery is improved. According to another technicalsolution in the prior art, a multilayered current collector is adopted,in which both sides of a resin layer are connected with metal layers toform a composite. When the temperature of the battery reaches a meltingpoint of the material of the resin layer, the resin layer of the currentcollector melts to damage the electrode plate, thereby cutting off thecurrent, and enhancing the safety of the battery.

However, these solutions in the related art cannot effectively preventthe occurrence of the internal short circuit in the lithium-ion battery,and cannot guarantee that the battery can continue to operate under theabnormal conditions. In the above solutions, the temperature in thebattery would still rise sharply after the internal short circuit occursin the battery. When the battery temperature rises sharply, if thesafety component fails to respond immediately, dangers of differentdegrees would still occur. In addition, in these solutions, even thesafety component responds and successfully avoids the hazard of thebattery, the battery still cannot continue to operate.

Therefore, it is necessary to provide a design of a current collectorand a battery that can effectively prevent accidents such as firing andexplosion caused by the occurrence of the internal short circuit underthe abnormal conditions such as collision, extrusion or puncture,without affecting the normal operation of the battery.

SUMMARY

The present disclosure provides a current collector, an electrode plateincluding the current collector, and an electrochemical device.

A first aspect of the present disclosure provides current collector. Thecurrent collector includes: an insulation layer; and a conductive layerat least located on at least one surface of the insulation layer. Theconductive layer has a thickness of D2, wherein 30 nm≤D2≤3 μm. Thecurrent collector is provided with a plurality of holes penetratingthrough the insulation layer and the conductive layer.

A second aspect of the present disclosure provides an electrode plateincluding the current collector according to the first aspect.

A third aspect of the present disclosure provides an electrochemicaldevice including the electrode plate according to the second aspect.

The technical solutions of the present disclosure have at least thefollowing beneficial effects.

In the current collector according to present disclosure, a conductivelayer is arranged on the surface of the insulation layer, and theconductive layer has a thickness of D2, which satisfies 30 nm≤D2≤3 μm.On one hand, due to the existence of the thin conductive layer and theinsulation layer in the current collector according to the presentdisclosure, a short-circuit resistance can be increased in the event ofthe short circuit under abnormal conditions of the battery, so that theshort-circuit current and the short-circuit heats generated during theshort circuit are greatly reduced, thereby improving the safetyperformance of the battery. On the other hand, the conductive layer ofthe current collector of the present disclosure is thin, the metal burrsoccurring inside the battery cell under abnormal conditions such asnailing may be small, which can reduce the risk of short circuit causedby the metal burrs piercing the separator and then contacting thenegative electrode directly, and thus improve the safety performance ofthe battery.

Moreover, providing the current collector with the plurality of holespenetrating through the insulation layer and the conductive layer canfacilitate stress relief of the conductive layer, thereby greatlyimproving a binding force between the conductive layer and theinsulation layer. Secondly, in abnormal conditions such as nailing, thenumber of metal burrs occurring inside the battery cell can be reduced,which can further improve the safety performance of the battery.Thirdly, the arrangement of the holes can facilitate electrolyte passingthrough and improve wettability of electrolyte based on electrodes ofthe current collector, thereby reducing polarization of the electrodesand the battery and improving electrochemical properties of the batterysuch as properties of charge-discharge at high rate and cycle life.Fourthly, providing the plurality of holes in the current collector canfurther reduce the weight of the current collector and increase theweight energy density of the battery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of a positive current collector according to anembodiment of the present disclosure;

FIG. 2 is a section view of the positive current collector as shown inFIG. 1;

FIG. 3 is a three-dimensional section view of the positive currentcollector as shown in FIG. 1;

FIG. 4 is a structural schematic diagram of another positive currentcollector according to an embodiment of the present disclosure;

FIG. 5 is a top view of another positive current collector according toan embodiment of the present disclosure;

FIG. 6 is a section view of the positive current collector as shown inFIG. 5;

FIG. 7 is a three-dimensional section view of the positive currentcollector as shown in FIG. 5;

FIG. 8 is a top view of another negative current collector according toan embodiment of the present disclosure;

FIG. 9 is a section view of the negative current collector as shown inFIG. 8;

FIG. 10 is a three-dimensional section view of the negative currentcollector as shown in FIG. 8;

FIG. 11 is a section view of a positive electrode plate according to anembodiment of the present disclosure;

FIG. 12 is a section view of another negative electrode plate accordingto an embodiment of the present disclosure; and

FIG. 13 is a schematic diagram of a nailing experiment according to thepresent disclosure (without holes illustrated).

REFERENCE SIGNS

-   -   1—positive electrode plate;        -   10—positive current collector;            -   101—positive insulation layer;            -   102—positive conductive layer;        -   11—positive active material layer;        -   201—hole;    -   2—negative electrode plate;        -   20—negative current collector;            -   201—negative insulation layer;            -   202—negative conductive layer;        -   21—negative active material layer;        -   401—hole;    -   3—separator;    -   4—nail.

DESCRIPTION OF EMBODIMENTS

The present disclosure is further described below by means ofembodiments. It should be understood that these embodiments are merelyused for illustrating the present disclosure, but not intended to limitthe present disclosure.

The structure and properties of the current collector according to thefirst aspect of the embodiments of the present disclosure will bedescribed in details below.

The present disclosure relates to a current collector. The currentcollector includes an insulation layer and a conductive layer located onat least one surface of the insulation layer. The conductive layer has athickness of D2, and 30 nm≤D2≤3 μm. The current collector is providedwith a plurality of holes penetrating through the insulation layer andthe conductive layer.

The insulation layer is used to support the conductive layer, and theconductive layer is used to support an electrode active material layer.

The insulation layer of the current collector according to the presentdisclosure is non-conductive and the conductive layer of the currentcollector according to the present disclosure is thin (30 nm≤D2≤3 μm),so its resistance is large. This can increase a short-circuit resistanceof the battery when the short circuit occurs under abnormal conditions,such that the short circuit current can be greatly reduced, and thus theheat generated by the short circuit can be greatly reduced, therebyimproving the safety performance of the battery.

On the other hand, due to the thin conductive layer of the currentcollector in the present disclosure, the metal burrs occurring insidethe battery cell under abnormal conditions such as nailing may be small,which can reduce the risk of short circuit caused by the metal burrspiercing the separator and then contacting the negative electrodedirectly, and thus improve the safety performance of the battery.

Moreover, the weight energy density of the battery can be increased byreplacing the conventional current collector of a metal foil with thecomposite current collector of the insulation layer and the conductivelayer.

Further, providing the current collector with the plurality of holespenetrating through the insulation layer and the conductive layer canfacilitate stress relief of the conductive layer, thereby greatlyimproving a binding force between the conductive layer and theinsulation layer and thus improving the long-term reliability andservice life of the current collector according to the presentdisclosure.

Further, in abnormal conditions such as nailing, the number of burrs,especially metal burrs, occurring when a foreign material pierces theconductive layer and the insulation layer of the current collector canbe reduced, which can reduce the risk of short circuit caused by themetal burrs piercing the separator and then contacting the negativeelectrode directly, and thus improve the safety performance of thebattery.

Moreover, the arrangement of the holes can facilitate electrolytepassing through and improve wettability of electrolyte based onelectrodes of the current collector, thereby reducing polarization ofthe electrodes and the battery and improving electrochemical propertiesof the battery such as properties of charge-discharge at high rate andcycle life.

Moreover, providing the plurality of holes in the current collector canfurther reduce the weight of the current collector and increase theweight energy density of the battery.

The holes have an aperture in a range from 0.001 mm to 3 mm. In thisrange, not only the effects of improving safety and polarization can beachieved, but also it is easier to process the current collector, andbreakage and the like is unlikely to occur during the processing.

An area ratio of the holes to an entire surface of the conductive layerdisposed on one surface of the insulation layer is 0.01% to 10%. Withinthis range, not only the effects of improving safety and polarizationcan be achieved, but also it is easier to process the current collector,and breakage and the like is unlikely to occur during the processing.

A spacing between two of the holes is in a range from 0.2 mm to 5 mm.The holes be equally spaced apart from one another or can be in amulti-pitch distribution within the range. As an example, the holes areequally spaced apart from one another.

The shape of the hole may be one of a parallelogram, a parallel-likequadrilateral, a circle, a circle-like, an ellipse, and an ellipse-likeshape.

As an example, the conductive layer is not only located on at least onesurface of the insulation layer, but also located on wall surfaces ofthe plurality of holes, and for each of the plurality of holes havingthe conductive layer disposed on its wall surface, the conductive layeris located on an entirety or a part of the wall surface of the hole.

As an example, a part of the conductive layer located on at least onesurface of the insulation layer is partially or entirely connected to apart of the conductive layer located on the wall surfaces of the holes.

In an implementation, the conductive layer is disposed on the uppersurface and the lower surface of the insulation layer and is alsodisposed on wall surfaces of the plurality of holes, and for each of theplurality of holes having the conductive layer disposed on its wallsurface, the conductive layer is located on an entirety or a part of thewall surface. In an example, a part of the conductive layer located onthe upper surface and the lower surface of the insulation layer ispartially or entirely connected to a part of the conductive layerlocated on the wall surfaces of the holes.

Therefore, the conductive layer firmly “grips” the insulation layer fromthe at least one surface of the insulation layer and the plurality ofholes. The bonding between the insulation layer and the conductive layeris not limited to the plane direction, but also the depth direction,which can strengthen the bonding force between the conductive layer andthe insulation layer, thereby improving the long-term reliability andservice life of the current collector. Especially when the conductivelayer is disposed on the upper surface and the lower surface of theinsulation layer and wall surfaces of the plurality of holes, thebonding between the conductive layer and the insulation layer may bestronger.

Moreover, in the current collector, since the insulation isnon-conductive and the conductive layer is thin, the conductivityproperty becomes a “letdown” of the composite current collector. Byproviding the conductive layer on the at least one surface of theinsulation layer and the wall surfaces of the plurality of holes, athree-dimensional conductive network having multiple point positions canbe formed in the current collector. This can greatly improve theconductivity property of the composite current collector, reduce thepolarization of the electrode plate and the battery, and improveelectrochemical properties of the battery such as properties ofcharge-discharge at high rate and cycle life.

It should be understood that the part of the conductive layer located onthe wall surfaces of the plurality of holes and the part of theconductive layer located on at least one surface of the insulation layermay have a same thickness or different thicknesses, and may be made of asame material or different materials. For each of the plurality of holeshaving the conductive layer disposed on its wall surface, the conductivelayer is located on an entirety or a part of the wall surface,preferably on an entirety of the wall surface. As an example, a part ofthe conductive layer located on at least one surface of the insulationlayer is partially or entirely connected to a part of the conductivelayer located on the wall surfaces of the holes.

Insulation Layer

In the current collector according to the embodiments of the presentdisclosure, the insulation layer mainly serves to support and protectthe conductive layer and has a thickness of D1, where 1 μm≤D1≤20 μm. Ifthe insulation layer is too thin, it is likely to be broken during theprocessing process of the electrode plate. If the insulation layer istoo thick, a volume energy density of the battery adopting this currentcollector may be reduced.

An upper limit of the thickness D1 of the insulation layer may be 20 μm,15 μm, 12 μm, 10 μm, or 8 μm. A lower limit of the thickness D1 of theinsulation layer may be 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, or 7μm. The thickness D1 of the insulation layer is in a range consisting ofany one upper limit and any one lower limit, preferably, 10 μm, and morepreferably, 2 μm≤D1≤6 μm.

The insulation layer is made of a material selected from a groupconsisting of an organic polymer insulation material, an inorganicinsulation material, a composite material, and combinations thereof.Preferably, the composite material includes an organic polymerinsulation material and an inorganic insulation material.

The organic polymer insulation material is selected from a groupconsisting of polyamide (abbreviated as PA), polyethylene terephthalate(abbreviated as PET), polyimide (abbreviated as PI), polyethylene(abbreviated as PE), polypropylene (abbreviated as PP), polystyrene(abbreviated as PS), polyvinyl chloride (abbreviated as PVC),acrylonitrile butadiene styrene copolymers (abbreviated as ABS),polybutylene terephthalate (abbreviated as PBT), poly-p-phenyleneterephthamide (abbreviated as PPA), epoxy resin, poly polyformaldehyde(abbreviated as POM), phenol-formaldehyde resin, ethylene propylenerubber (abbreviated as PPE), polytetrafluoroethylene (abbreviated asPTFE), silicone rubber, polyvinylidene fluoride (abbreviated as PVDF),polycarbonate (abbreviated as PC), aramid fiber,polydiformylphenylenediamine, cellulose and derivatives thereof, starchand derivatives thereof, proteins and derivatives thereof, polyvinylalcohol and crosslinked products thereof, polyethylene glycol andcrosslinked products thereof, and combinations thereof.

The inorganic polymer insulation material is selected from a groupconsisting of Al₂O₃, SiC, SiO₂, and combinations thereof.

The composite material is preferably selected from a group consisting ofepoxy resin glass fiber reinforced composite material, polyester resinglass fiber reinforced composite material, and combinations thereof.

Preferably, the material of the insulation layer is selected from theorganic polymer insulation materials. Since the insulation layer usuallyhas a smaller density than the metal, the current collector according tothe present disclosure can improve the weight energy density of thebattery while improving the safety performance of the battery. Inaddition, since the insulation layer can well support and protect theconductive layer located on the surface thereof, a breakage of theelectrode, which is common in the conventional current collector, isunlikely to occur.

Conductive Layer

In the current collector according to the embodiments of the presentdisclosure, the conductive layer has a thickness of D2, and 30 nm≤D2≤3μm.

The conductive layer is made of a material selected from a groupconsisting of a metal conductive material, a carbon-based conductivematerial, and combinations thereof. The metal conductive material ispreferably selected from a group consisting of aluminum, copper, nickel,titanium, silver, nickel-copper alloy, aluminum-zirconium alloy, andcombinations thereof. The carbon-based conductive material is preferablyselected from a group consisting of graphite, acetylene black, graphene,carbon nanotubes, and combinations thereof.

In the existing lithium-ion batteries in which an Aluminum foil or acopper foil is used as a current collector, when an internal shortcircuit occurs in the battery under an abnormal situation, a largecurrent would be instantaneously generated, a large quantity of heat isgenerated by the short circuit correspondingly. The heat usually furtherresults in aluminothermal reaction at the positive current collectormade of aluminum foil, which can cause the firing, explosion, etc. ofthe battery.

In the embodiments of the present disclosure, the above technicalproblems are solved by using a current collector, in which an insulationlayer serves as a support and the conductive layer has a specificthickness (30 nm≤D2≤3 μm). Since the insulation layer is non-conductiveand the conductive layer is much thinner than the conventional currentcollector (which has a thickness of about 9 μm to 14 μm), the currentcollector has a relatively high resistance. In this way, in the event ofthe short circuit under abnormal conditions of the battery, ashort-circuit resistance can be increased, so that the short-circuitcurrent and thus the generated short-circuit heat can be greatlyreduced, thereby improving the safety performance of the battery.

Generally, the internal resistance of the battery includes ohmicinternal resistance of the battery and internal resistance of thebattery polarization. The resistances of the active material, currentcollector and interface, and the electrolyte composition all have asignificant influence on the internal resistance of the battery. In theevent of the short circuit under abnormal conditions, the internalresistance of the battery will be greatly reduced due to the occurrenceof the internal short circuit. Therefore, by increasing the resistanceof the current collector, the internal resistance of the battery in theevent of the short circuit can be increased, thereby improving thesafety performance of the battery.

The conductive layer has a thickness which is sufficient to have effectsof conduction and current collection. If the thickness of the conductivelayer is too small, the effects of conduction and current collection aretoo poor, the polarization of the battery can be severe, and theconductive layer is also likely to be damaged during the processingprocess of the electrode plate. If the thickness of the conductive layeris too large, a weight energy density of the battery can be affected,and it is not conducive to improving the safety performance of thebattery.

An upper limit of the thickness D2 of the conductive layer may be 3 μm,2.8 μm, 2.5 μm, 2.3 μm, 2 μm, 1.8 μm, 1.5 μm, 1.2 μm, 1 μm, or 900 nm. Alower limit of the thickness D2 of the conductive layer may be 800 nm,700 nm, 600 nm, 500 nm, 450 nm, 400 nm, 350 nm, 300 nm, 250 nm, 200 nm,150 nm, 100 nm, or 30 nm. The thickness of the conductive layer is in arange consisting of any one upper limit and any one lower limit,preferably, 300 nm≤D2≤2 μm, and more preferably, 500 nm≤D2≤1.5 μm.

The conductive layer can formed on the insulation layer by means of atleast one of vapor deposition and electroless plating. With respect tothe vapor deposition, physical vapor deposition (PVD) is preferable.Preferably, the physical vapor deposition is at least one of evaporationdeposition and sputtering deposition. As regards the evaporationdeposition, at least one of vacuum evaporation, thermal evaporationdeposition, electron beam evaporation method (EBEM) is preferable. Asregards the sputtering deposition, magnetron sputtering is preferable.

FIGS. 1-9 are schematic structural diagrams of current collectorsaccording to the embodiments of the present disclosure.

As shown in FIGS. 1-3, the positive current collector 10 includes apositive insulation layer 101 and a positive conductive layer 102provided on one surface of the positive insulation layer 101. Thepositive current collector 10 is provided with a plurality of holes 201penetrating through the positive insulation layer 101 and the positiveconductive layer 102, and the positive conductive layer 102 is notformed on wall surfaces of the holes 201.

As shown in FIG. 4, the positive current collector 10 includes apositive insulation layer 101 and a positive conductive layer 102provided on one surface of the positive insulation layer 101. Thepositive current collector 10 is provided with a plurality of holes 201penetrating through the positive insulation layer 101 and the positiveconductive layer 102, and the positive conductive layer 102 is alsolocated on all wall surfaces of the holes 201.

Referring to FIGS. 5-7, the positive current collector 10 includes apositive insulation layer 101 and a positive conductive layer 102provided on one surface of the positive insulation layer 101. Thepositive current collector 10 is provided with a plurality of holes 201penetrating through the positive insulation layer 101 and the positiveconductive layer 102. The positive conductive layer 102 is also locatedon a part of wall surfaces of the holes 201, and a part of the positiveconductive layer 102 located on the wall surfaces is connected to a partof the positive conductive layer 102 located on the surface of thepositive insulation layer 101.

Referring to FIGS. 8-10, the negative current collector 20 includes anegative insulation layer 201 and a negative conductive layer 202provided on two opposite surfaces of the negative insulation layer 201.The negative current collector 20 is provided with a plurality of holes401 penetrating through the negative insulation layer 201 and thenegative conductive layer 202. The negative conductive layer 202 is alsolocated on all wall surfaces of the holes 401, and a part of thenegative conductive layer 202 located on the negative insulation layer201 is connected to a part of the negative conductive layer 202 locatedon the on the wall surfaces.

The second aspect of the present disclosure provides an electrode plate.The electrode plate includes the current collector according to thefirst aspect of the present disclosure and an electrode active materiallayer formed on the current collector.

FIG. 11 is a schematic structural diagram of a positive electrode plateaccording to an embodiment of the present disclosure. As shown in FIG.11, the positive electrode plate 1 includes a positive current collector10 and a positive active material layer 11 formed on a surface of thepositive current collector 10. The positive current collector 10includes a positive insulation layer 101 and a positive conductive layer102 disposed on two opposite surfaces of the positive insulation layer101. The positive current collector 10 is provided with a plurality ofholes 201 penetrating through the positive insulation layer 101 and thepositive conductive layer 102. The positive conductive layer 102 is alsolocated on all wall surfaces of the plurality of holes 201, and a partof the positive conductive layer 102 located on the positive insulationlayer 101 is connected to a part of the positive conductive layer 102located on the wall surfaces of the holes. The positive active materiallayer 11 is disposed on the positive conductive layer 102 and covers theplurality of holes 201, but is not filled in the plurality of holes 201.In practice, after being coated or dried and then compacted, thepositive active material layer 11 may intrude into the holes throughopenings of the holes.

FIG. 12 is a schematic structural diagram of a negative electrode plateaccording to embodiments of the present disclosure. As shown in FIG. 12,the negative electrode plate 2 includes a negative current collector 20and a negative active material layer 21 formed on a surface of thenegative current collector 20. The negative current collector 20includes a negative insulation layer 201 and two negative conductivelayers 202 disposed on two opposite surfaces of the negative insulationlayer 201. The negative current collector 20 is provided with aplurality of holes 401 penetrating through the negative insulation layer201 and the negative conductive layer 202. The negative conductive layer202 is also located on all wall surfaces of the plurality of holes 401,and a part of the negative conductive layer 202 located on the negativeinsulation layer 201 is connected to a part of the negative conductivelayer 202 located on the wall surfaces of the holes. The negative activematerial layer 21 is disposed on the negative conductive layer 202 andis filled in the plurality of holes 401.

It should be noted that FIGS. 1-12 are merely illustrative, and sizes,shapes and arrangements of the holes in the drawings are allillustrative.

It would be appreciated that when the conductive layer is arranged onboth two opposite surfaces of the insulation layer, the currentcollector is coated with the active material on its two surfaces and themanufactured positive and negative electrode plates can be directlyapplied in the electrochemical device; and when the conductive layer isarranged on one surface of the insulation layer, the current collectoris coated with the active material on its one surface and themanufactured positive and negative electrode plates can be applied inthe battery after being folded.

The electrode active material layer can be formed on at least onesurface of the current collector. In this case, the electrode activematerial layer is arranged on the surface of the current collector andcovers the plurality of holes. As an example, when the conductive layeris arranged on the wall surfaces of the holes and the holes have anaperture not larger than 35 μm, the electrode active material layer canbe formed on the at least one surface of the current collector and groutleaking is unlikely to occur. After being dried and compacted, theelectrode active material layer may intrude into the holes throughopenings of the holes.

In an example, the electrode active material layer is formed on at leastone surface of the current collector, and can be entirely or partiallyfilled in the plurality of holes of the current collector. Preferably,the electrode active material layer formed on at least one surface ofthe current collector and the electrode active material layer filled inthe plurality of holes of the current collector are partially orentirely connected to each other. In this way, the bonding force betweenthe electrode active material layer and the current collector isstronger, and the long-term reliability and service life of theelectrode plate and the battery can be improved. In addition, since theelectrode active material layer has a certain porosity, such arrangementcan have better electrolyte wettability and smaller polarization ascompared with an electrode plate formed by a composite current collectorof a pore less structure.

The embodiments of the present disclosure also provide anelectrochemical device. The electrochemical device includes a positiveelectrode plate, a separator and a negative electrode plate. Theelectrochemical device can be a wound type or a laminated type battery,such as one of a lithium ion secondary battery, a primary lithiumbattery, a sodium ion battery, or a magnesium ion battery. However, itis not limited to these batteries.

The positive electrode plate and/or the negative electrode plate are theelectrode plate according to the above embodiments of the presentdisclosure.

As an example, the positive electrode plate of the battery according tothe present disclosure employs the electrode plate according to thepresent disclosure. Since the conventional positive current collectorhas a high aluminum content, when the short circuit occurs under theabnormal condition of the battery, the heat generated at theshort-circuit point can cause a severe aluminothermal reaction, whichgenerates a huge amount of heat and further causes the explosion orother accidents of the battery. When the battery adopts the positiveelectrode plate according to the present disclosure, the aluminothermalreaction can be avoided due to the greatly reduced aluminum content inthe positive current collector, thereby significantly improving thesafety performance of the battery. The current collector is providedwith a plurality of holes penetrating through the insulation layer andthe conductive layer, thereby facilitating the electrolyte passingthrough, improving wettability of the electrolyte based on electrodes ofthe current collector, thereby reducing polarization of the electrodesand the battery and improving electrochemical properties of the batterysuch as properties of charge-discharge at high rate and cycle life.Moreover, providing the plurality of holes in the current collector canfurther reduce the weight of the current collector and increase theweight energy density of the battery.

In the present disclosure, a nailing experiment is used to simulate theabnormal conditions of the battery and observe a change of the batteryafter the nailing. FIG. 13 is a schematic diagram of a nailingexperiment according to the present disclosure. For the reason ofsimplicity, FIG. 13 merely illustrates that a nail 4 punctures one layerof positive electrode plate 1, one layer of separator 3 and one layer ofnegative electrode plate 2 of the battery. It should be clear that inthe actual nailing experiment, the nail 4 penetrates the entire battery,which generally includes a plurality of layers of positive electrodeplate 1, a plurality of layers of separator 3 and a plurality of layersof negative electrode plate 2. When a short circuit occurs in thebattery due to the nailing, the short-circuit current is greatlyreduced, and the heat generated during the short circuit is controlledwithin a range that the battery can fully absorb. Therefore, the heatgenerated at the position where the internal short-circuit occurs can becompletely absorbed by the battery, and the increase in temperature isalso very small, so that the damage on the battery caused by the shortcircuit can be limited to the nailing position, and only a “point break”can be formed without affecting the normal operation of the battery in ashort time.

EMBODIMENTS

1. Preparation of Current Collector

1.1 An insulation layer having a certain thickness is selected,perforation is performed in the insulation layer to form holes, and thena conductive layer having a certain thickness is formed by means ofvacuum evaporation in such a manner that the conductive layer isdeposited on at least one surface of the insulation layer and the wallsurfaces of the holes.

1.2 An insulation layer having a certain thickness is selected, aconductive layer having a certain thickness is formed by means of vacuumevaporation on a surface of the insulation layer, and then perforationis performed to form holes penetrating through the insulation layer andthe conductive layer.

1.3 An insulation layer having a certain thickness is selected,perforation is performed to form holes, and then a conductive layer isdeposited on the surface of the plane and the wall surfaces of the holesor on the wall surfaces of the holes and the surface of the plane.

The conditions of the vacuum evaporation for forming the conductivelayer are as follows: the insulation layer is placed in a vacuumevaporation chamber after a surface cleaning treatment, a high-puritymetal wire in a metal evaporation chamber is melted and evaporated at ahigh temperature in a range of 1600° C. to 2000° C., the evaporatedmetal passes through a cooling system in the vacuum evaporation chamberand is finally deposited on a surface of the insulation layer, so as toform the conductive layer.

2. Preparation of Electrode Plate

Positive slurry or negative slurry is coated on a surface of the currentcollector by a conventional coating process of battery and dried at 100°C., so as to obtain a positive electrode plate or a negative electrodeplate.

Conventional positive electrode plate: current collector is an Al foilwith a thickness of 12 μm, and the electrode active material layer is aternary (NCM) material layer having a certain thickness.

Conventional negative electrode plate: current collector is a Cu foilwith a thickness of 8 μm, and the electrode active material layer is agraphite layer having a certain thickness.

In some embodiments, the electrode active material layer is disposedonly in a planar portion of the current collector. In some embodiments,the electrode active material layer is disposed in a planar portion theholes of the current collector.

The specific parameters of the prepared current collector and itselectrode plates are shown in Table 1. Parameters of the insulationlayer, the conductive layer and the electrode active material parametersof the current collector of Electrode Plates 1 to 8 are shown in Table1, in which the conductive layer is disposed on the upper surface andthe lower surface of the insulation layer, and the conductive layer isformed by means of vacuum evaporation. “Surface only” means that thecurrent collector is provided with a plurality of holes penetratingthrough the insulation layer and the conductive layer, and theconductive layer is disposed only on the upper surface and the lowersurface of the insulation layer. “Surface and holes” means that thecurrent collector is provided with a plurality of holes penetratingthrough the insulation layer and the conductive layer, the conductivelayer is disposed not only on the upper surface and the lower surface ofthe insulation layer but also on all wall surfaces of the holes, and apart of the conductive layer formed on the wall surfaces of the holes isconnected to a part of the conductive layer formed on the surface of theinsulation layer. The holes are circular and have an aperture of 0.01mm, the area ratio of the holes is selected to be 5%, and a spacingbetween two of the holes is 0.2 mm. The electrode active material isfilled in a plurality of holes.

3. Preparation of Battery:

According to a conventional battery preparing process, a positiveelectrode plate (compaction density: 3.4 g/cm³), a PP/PE/PP separatorand a negative electrode plate (compaction density: 1.6 g/cm³) togetherare winded to form a bare cell, then the bare cell is placed into abattery case, an electrolyte (EC:EMC in a volume ratio of 3:7, LiPF₆:1mol/L) is injected into the case, following by sealing, formation, andthe like, so as to obtain a lithium-ion secondary battery.

Specific compositions of the batteries prepared in the embodiments ofthe present disclosure and the batteries of the Comparative Examples areshown in Table 2.

TABLE 1 With or Electrode active Electrode Insulation Layer ConductiveLayer without material layer Plate No. Material D1 Material D2 holesStates of holes Material Thickness Electrode PI 6 μm Al 2 μm Without /NCM 55 μm Plate 1 holes Electrode PET 1 μm Al 30 nm With holes Surfaceonly LCO 55 μm Plate 2 Electrode PI 2 μm Al 300 nm With holes Surfaceand NCM 55 μm Plate 3 holes Electrode PET 10 μm Al 500 nm With holesSurface and NCM 55 μm Plate 4 holes Electrode PET 8 μm Ni 800 nm Withholes Surface and NCM 55 μm Plate 5 holes Electrode PI 20 μm Al 1 μmWith holes Surface and NCM 55 μm Plate 6 holes Electrode PET 6 μm Al 1.5μm With holes Surface and NCM 55 μm Plate 7 holes Electrode PET 6 μm Al2 μm With holes Surface and NCM 55 μm Plate 8 holes

TABLE 2 Battery No. Composition of Electrodes Battery 1 conventionalpositive conventional negative electrode plate electrode plate Battery 2electrode plate 1 conventional negative electrode plate Battery 3electrode plate 2 conventional negative electrode plate Battery 4electrode plate 3 conventional negative electrode plate Battery 5electrode plate 4 conventional negative electrode plate Battery 6electrode plate 5 conventional negative electrode plate Battery 7electrode plate 6 conventional negative electrode plate Battery 8electrode plate 7 conventional negative electrode plate Battery 9electrode plate 8 conventional negative electrode plate

EXPERIMENTAL EXAMPLES

1. Test Methods of Cycle Life of Battery:

A method for testing cycle life of the lithium-ion battery was performedas follows:

A lithium-ion battery was charged and discharged at 25° C. and 45° C.,respectively, i.e., the battery was firstly charged with a current of 1C to a voltage of 4.2V, then was discharged with a current of 1 C to avoltage of 2.8V, and the discharge capacity after a first cycle wasrecorded; and the battery was charged and discharged for 1000 cycles asabove, and the discharge capacity of the battery after a 1000th cyclewas recorded. A capacity retention rate after the 1000^(th) cycle wasobtained by dividing the discharge capacity after the 1000^(th) cycle bythe discharge capacity after the first cycle.

The experimental results are shown in Table 3.

2. Test Methods of Nailing Experiment:

Nailing Experiment: a battery that had been fully charged was fixed, asteel needle with a diameter of 8 mm punctured through the battery at aspeed of 25 mm/s at room temperature and remained in the battery, andthe battery was observed and measured after the nailing was finished.

Measurement of Battery Temperature: a multichannel thermometer was used,and the temperature sensing wires were respectively attached ongeometric centers of a nail-inserting surface and an opposite surface ofthe battery to be nailed; after the nailing was finished, temperature ofthe battery was measured and tracked for 5 minutes, and the temperaturesof the battery at the end of 5 minutes were recorded.

Measurement of Battery Voltage: positive and negative electrodes of eachbattery to be nailed were connected to test terminals of an internalresistance instrument; after the nailing was finished, voltage of eachbattery was measured and tracked for 5 minutes, and the voltage of thebattery at the end of 5 minutes was recorded.

Data of the recorded temperatures and voltages of the batteries areshown in Table 4.

3. Test Methods of Bonding Force between Conductive Layer and InsulationLayer:

The electrode plate was immersed in a mixed solvent of dimethylcarbonate and hydrofluoric acid, in which content of the hydrofluoricacid was 0.1 wt %, and then was vacuum-sealed and stored in a 70° C.incubator for several days. After the storage, the electrode plate wastaken out, and folded in half along a length direction. At the sametime, a 2 Kg weight was placed on the fold to compact it for 10 seconds.After the compaction, the electrode plate was flattened and thenobserved to see if the conductive layer peels off at the fold, and thenumber of days for which the electrode plate had been stored before thepeeling off started to appear was recorded. The test results are shownin Table 5.

TABLE 3 Capacitance Retention Rate at the 1000^(th) Cycle Battery No.25° C. 45° C. Battery 1 87.9% 83.2% Battery 2 81.3% 78.1% Battery 384.6% 80.2% Battery 4 86.7% 81.5% Battery 5 87.9% 82.1% Battery 6 88.0%83.2% Battery 7 87.8% 82.8% Battery 8 88.0% 82.6% Battery 9 87.8% 82.4%

TABLE 4 Nailing Experiment Batter Temperature Rise Battery VoltageBattery No. (° C.) (V) Battery 1 N/A N/A Battery 2 17.2 3.85 Battery 32.3 4.13 Battery 4 2.9 4.13 Battery 5 5.0 4.11 Battery 6 5.6 4.10Battery 7 8.9 3.97 Battery 8 11.7 3.91 Battery 9 14.1 3.89 “N/A”indicates that thermal runaway and damage happened immediately after asteel needle punctured through the battery.

TABLE 5 Electrode Plate No. Number of Days Electrode Plate 1 10Electrode Plate 2 18 Electrode Plate 3 >30 Electrode Plate 4 >30Electrode Plate 5 >30 Electrode Plate 6 >30 Electrode Plate 7 >30Electrode Plate 8 >30

From the results in Table 4, it can be seen that, as regards Battery 1which does not adopting the current collector according to theembodiments of the present disclosure (i.e., the battery formed byadopting the conventional positive electrode plate and the conventionalnegative electrode plate), the temperature increased abruptly byhundreds of degree Celsius and the voltage dropped abruptly to zero atthe moment of nailing. This shows that an internal short circuitoccurred at the moment of nailing, a large amount of heats wasgenerated, a thermal runaway and damage of the battery instantlyoccurred, so that the battery is unable to continue operating.

Compared with a battery formed by a conventional positive electrodeplate and a conventional negative electrode plate, the composite currentcollector according to the present disclosure can greatly improve thesafety performance of the battery, and the smaller thickness of theconductive layer can lead to the more obvious improvement effect onsafety. In addition, the composite current collector with holes may bemore conductive to an improvement in safety performance as compared to acomposite current collector without holes.

It can be seen from the results in Table 4 that, compared with thebattery adopting the conventional positive electrode plate and theconventional negative electrode plate, the batteries adopting thecurrent collectors according to the embodiments of the presentdisclosure have a good cycle performance, which is equivalent to thecycle performance of a conventional battery. This shows that the currentcollectors according to the embodiments of the present disclosure do nothave any significantly adverse influence on the resulting electrodeplates and batteries.

It can be seen from the results in Table 5 that in the composite currentcollector having holes, the bonding force between the conductive layerand the insulation layer is significantly enhanced with respect to thecomposite current collector without holes. In particular, when theconductive layer is disposed on the surface of the insulation layer andthe wall surfaces of the plurality of holes, the conductive layer firmly“grips” the insulation layer from at least one surface of the insulationlayer and the plurality of holes. The bonding between the insulationlayer and the conductive layer is not limited to the plane direction,but also the depth direction, which can strengthen the bonding forcebetween the conductive layer and the insulation layer, thereby improvingthe long-term reliability and service life of the current collector.

The preferable embodiments of the present disclosure are disclosed abovebut are not used to limit the claims. Those skilled in the art may makepossible changes and modifications without departing from the concept ofthe present disclosure. Therefore, the protection scope of the presentdisclosure is defined by the attached claims.

What is claimed is:
 1. An electrochemical device, comprising a positiveelectrode plate, a negative electrode plate, and a separator disposedbetween the positive electrode plate and the negative electrode plate,wherein the positive electrode plate and/or the negative electrode platecomprises a current collector and an electrode active material layer atleast formed on at least one surface of the current collector, whereinthe current collector comprises: an insulation layer; and a conductivelayer at least located on at least one surface of the insulation layer,wherein the conductive layer has a thickness of D2, where 30 nm≤D2≤3 μm,wherein a plurality of through holes each penetrates through theinsulation layer and the conductive layer, wherein the electrode activematerial layer is further filled in the plurality of through holes, andwherein a part of the electrode active material layer formed on the atleast one surface of the current collector is partially or entirelyconnected to a part of the electrode active material layer filled in theplurality of through holes.
 2. The electrochemical device according toclaim 1, wherein the conductive layer is further arranged on wallsurfaces of the plurality of through holes, and for each of theplurality of through holes having the conductive layer disposed on itswall surface, the conductive layer is located on a part or an entiretyof the wall surface.
 3. The electrochemical device according to claim 2,wherein a part of the conductive layer located on the at least onesurface of the insulation layer is partially or entirely connected to apart of the conductive layer located on the wall surfaces of theplurality of through holes; and preferably, the at least one surface ofthe insulation layer comprises an upper surface and a lower surface ofthe insulation layer, and a part of the conductive layer located on theupper surface and the lower surface of the insulation layer is partiallyor entirely connected to the part of the conductive layer located on thewall surfaces of the plurality of through holes.
 4. The electrochemicaldevice according to claim 1, wherein 300 nm≤D2≤2 μm.
 5. Theelectrochemical device according to claim 1, wherein 500 nm≤D2≤1.5 μm.6. The electrochemical device according to claim 1, wherein theconductive layer is made of a material selected from a group consistingof a metal conductive material, a carbon-based conductive material, andcombinations thereof, wherein the metal conductive material ispreferably selected from a group consisting of aluminum, copper, nickel,titanium, silver, nickel-copper alloy, aluminum-zirconium alloy, andcombinations thereof, and wherein the carbon-based conductive materialis preferably selected from a group consisting of graphite, acetyleneblack, graphene, carbon nanotubes, and combinations thereof.
 7. Theelectrochemical device according to claim 1, wherein the insulationlayer has a thickness of D1, and wherein 1 μm≤D1≤20 μm.
 8. Theelectrochemical device according to claim 7, wherein 2 μm≤D1≤10 μm. 9.The electrochemical device according to claim 7, wherein 2 μm≤D1≤6 μm.10. The electrochemical device according to claim 1, wherein theinsulation layer is made of a material selected from a group consistingof an organic polymer insulation material, an inorganic insulationmaterial, a composite material, and combinations thereof, the organicpolymer insulation material is selected from a group consisting ofpolyamide, polyethylene terephthalate, polyimide, polyethylene,polypropylene, polystyrene, polyvinyl chloride, acrylonitrile butadienestyrene copolymers, polybutylene terephthalate, poly-p-phenyleneterephthamide, epoxy resin, polyformaldehyde, phenol-formaldehyde resin,ethylene propylene rubbe, polytetrafluoroethylene, silicone rubber,polyvinylidene fluoride, polycarbonate, aramid fiber,polydiformylphenylenediamine, cellulose and derivatives thereof, starchand derivatives thereof, proteins and derivatives thereof, polyvinylalcohol and crosslinked products thereof, polyethylene glycol andcrosslinked products thereof, and combinations thereof, the inorganicinsulation material is selected from a group consisting of aluminiumoxide, silicon carbide, silicon dioxide and combinations thereof, andthe composite material is selected from a group consisting of an epoxyresin glass fiber reinforced composite material, a polyester resin glassfiber reinforced composite material, and combinations thereof.
 11. Theelectrochemical device according to claim 10, wherein the insulationlayer is made of the organic polymer insulation material.